Leveling control for a press

ABSTRACT

A LEVELLING CONTROL FOR A PRESS HAVING A MOVEABLE PLATEN OPERATED BY A PAIR OF HYDRAULIC RAMS WHEREIN AN ELONGATED TORSION TUBE IS MOUNTED WITH ITS LONGITUDINAL AXIS HORIZONTAL ON THE MOVING PLATEN AND OPERATIVELY ASSOCIATED WITH MEANS TO CONTROL THE SUPPLY OF HYDRAULIC FLUID TO SAID RAMS IN RESPONSE TO TWISTING OF THE TORSION TUBE ABOUT ITS LONGITUDINAL AXIS.

United States Patent Inventor Eric George Krause Osborne Park, Australia Appl. No. 774,358 Filed Nov. 8, 1968 Patented June 28,1971 Assignee Nova Machinery Pty. Ltd.

Osborne Park, Australia Priority Nov. 15, 1967 Australia 29833/67 LEVELING CONTROL FOR A PRESS [56] References Cited UNITED STATES PATENTS 2,343,167 2/1944 Bench 100/258 2,377,007 5/1945 Hess..... 100/258 2,864,127 12/1958 Marti.... 100/258X 3,099,953 8/1963 Baauer 100/258 FOREIGN PATENTS 250,426 3/1964 Australia 100/258 Primary ExaminerBilly J. Wilhite Attorney Watson, Leavenworth and Kelton 5 Claims 7 Drawing Figs ABSTRACT: A levelling control for a press having a moveable [1.8. CI 100/256, platen operated by a pair of hydrauiic rams wherein an elon- 100/258, 100/269 gated torsion tube is mounted with its longitudinal axis lnt.Cl B30b 15/24 horizontal on the moving platen and operatively associated Field of Search 100/46, ith means to control the supply of hydraulic fluid to said 258, 158 (A), 256, 257, 269; 91/177; 83/624, 639; rams in response to twisting of the torsion tube about its lon- 72/441, 453 gitudinal axis.

PATENTEI] JUN28 IEIYI SHEET 2 OF 4 PATENIH] JUN28 ISM SHEET 3 OF 4 PATENTED JUNE 8 mm SHEET 0F 4 LEVELING CONTROL FOR A PRESS This invention relates to a levelling control for a press andiin particular relates to a control for maintaining parallelism between the fixed and moving beams or platens of presses similar to that described in Australian Pat. specification No. 250,426.

According to the present invention there is provided a levelling control for a press having a moveable platen operated by a pair of hydraulic rams, said levelling control comprising an elongated torsion member mounted with. its longitudinal axis horizontal on the moveable platen, and being free to rotate about said longitudinal axis, said torsion member having one end thereof attached to a fixed point of the press, the other end thereof being operatively connected to one or more hydraulic valves arranged to control the supply of hydraulic fluid to one or both of said hydraulic rams in response to twisting of said torsion member.

In one particular form there is provided a levelling control for a press having a moveable platen operated by a pair of hydraulic rams, said levelling control comprising an elongated torsion member mounted with its longitudinal axis horizontal on the moving platen of the press and being free to rotate about said longitudinal axis, a first lever arm fixed adjacent one end of said torsion member, said first lever arm being pivotally connected to a first link member, said first link member being pivotally connected to a fixed point on the press, and a second lever arm fixed adjacent the other end of said torsion member, said second lever arm being pivotally connected to a second link member, said second link member being connected to a hydraulic valve mounted in a fixed posi' tion on said press, said valve being adapted to be connected in circuit with either of said pair of hydraulic rams.

The invention may be better understood by reference to the following description of a preferred embodiment thereof as illustrated in the accompanying drawings in which:

FIG. 1 is a diagrammatic elevation of the levelling control fitted to a press;

FIG. 2 is a fragmentary sectional elevation on the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary sectional elevation on the line 33 of FIG. '1;

FIG. 4 is a fragmentary sectional elevation on the line 44, of FIG. 1;

FIG. Sis a fragmentary sectional elevation on the line 5-5. of FIG. 1; and

FIG. 6 is a fragmentary sectional elevation on the line 66 of FIG. 1.

FIG. 7 is a schematic depiction of the hydraulic circuit associated with the press shown in FIGS. 16.

In the embodiment shown in the drawings the press shown in dotted outline in FIG. 1, is provided with a moveable platen or beam 11 which moves up and down in a vertical plane under the control of a pair of hydraulic rams 12 and 13 one at each end of the beam 11. The beam 11 is provided with a light torsion or torque tube 14 supported at its end in antifriction bearings mounted on the moving beam 11, with its longitudinal axis substantially horizontal. A first lever arm 15 is fixed, as for example by welding, at one end of the torsion tube 14 whilst a second lever arm 16 is similarly provided adjacent the other end of the tube 14. The first lever arm 15 is pivotally connected by a pin joint to one end ofa first link member 17, the other end of the link member 17 being pivotally connected to a fixed reference point which in this embodiment is preferably the end frame of the press. The second lever arm 16 is pivotally connected to one end of a second link member 18, the other end of the link member 18 being adapted to operate a two-way hydraulic valve 19 connected in the hydraulic circuits of the rams 12 and 13.

While the moving beam 11 remains horizontal, the torsion tube 14 simply rotates about its longitudinal axis. If the beam or platen 11 tends to move away from the horizontal due to operation of one of the hydraulic rams 12 or 13 being faster or slower than the other, then the torsion tube 14 will tend to twist, sirice one end of the tube is connected to a fixed point through the lever arm 15 as seen in FIG. 2. The twisting ofthe torsion tube 14 is amplified by the lever arm 16 which will cause the valve 19 to operate to bleed the oil supply to the leading hydraulic ram, the valve 19 being caused to be connected into the circuit of the leading hydraulic ram due to the direction of twist of the torsion tube 14.

- Preferably, third and fourth lever arms 20 are fixed to the torsion tube 14 adjacent the first and second lever arms 15 and 16 respectively, the lever arms 20 being each connected via a connecting rod 21 to a limit switch 22, each limit switch 22 being associated with the pump supplying hydraulic fluid to the rams 12 and 13. The hydraulic valve 19 and the limit switches 22 are preferably mounted. on the hydraulic fluid reservoir.

If for any reason, the press tends to override the levelling control, the appropriate limit switch 22 is actuated to completely cut off the oil supply to the leading ram, until the platen 11 is again horizontal. Normally these limit switches 22 are only a safety feature since the valve 19 will normally main tain the platen 11 horizontal within extremely fine limits.

A further control may be provided if desired to ensure that the moving beam 11 is absolutely horizontal at the most critical point of the stroke, that is, at the point of reversal of its travel at the bottom of the stroke. This control comprises a further pair of limit switches 23 fitted one at each end of the moving beam 11. The fixed table 24 of the press is provided with a pair of substantially vertical fixed shafts 25 one at each end thereof each shaft 25 being provided with an adjustable lower limit stop 27 slidably mounted thereon and so located that the operating arm 26 of the limit switch 23 contacts the stop 27 at the point of reversal of the moving beam 11. The operating arms 26 of both of the switches 23 must be contacted before the moving beam 11 will reverse. The lower limit stop 27 is preferably adjusted by a rotating screw connected through a gear box 28 to a drive shaft 29 which is preferably rotated by a hand wheel 31) which allows both the stops 27 to be adjusted simultaneously. If desired an upper limit switch 31 may be provided at one end of the moving platen 11, the switch 31 being actuated by an upper limit stop 32 on one ofthe shafts 25.

The operation of the limit switches 23 is such that if one end of the platen 11 is leading even by as little as 0.002 inches, it will stop as soon as the associated limit switch is contacted and will not reverse until the lagging end contacts its associated switch 23, following which the platen 11 will reverse and return to the top of its stroke.

FIG. 7 shows the hydrauliccircuit associated with the leveling control of the present invention. Each hydraulic ram 12 and 13 has associated therewith its own hydraulic pump 112, 113 respectively, such pumps being operated by a motor 110. The portion of the circuit associated with each hydraulic ram also includes directional control valves 114 and 118 associated with the rams, the respective control valves being operated by means of solenoids 115, 116 and 120, 121 respectively. The solenoids in turn are energized and deenergized by means of the operation of limit switches 22, 23 and 31, the directional control valves thus being used for raising and lowering the press moveable platen for changing the direction of movement upwards and downwards of the press platen 11 when the appropriate switches are actuated. The hydraulic valve 19 which controls the operation of the hydraulic rams is utilized for controlling both rams with the same valve as indicated in FIG. 7.

Iclaim:

1. A levelling control for a press having a moveable platen operated by a pair of hydraulic rams, said levelling control comprising an elongated torsion member mounted with its longitudinal axis horizontal on the moveable platen and being free to rotate about said longitudinal axis, said torsion member having one end thereof attached to a fixed point of the press, a hydraulic valve, the other end of said torsion member being operatively connected to said hydraulic valve for controlling the supply of hydraulic fluid to said hydraulic rams in response to twisting of said torsion tube.

2. A levelling control for a press having a moveable platen operated by a pair of hydraulic rams, said levelling control comprising an elongated torsion member mounted with its longitudinal axis horizontal on the moving platen of the press and being free to rotate about said longitudinal axis, a first lever arm fixed adjacent one end of said torsion member, said first lever arm being pivotally connected to a first link member, said first link member being pivotally connected to a fixed point on the press, and a second lever arm fixed adjacent the other end of said torsion member, said second lever arm being pivotally connected to a second link member, a hydraulic valve mounted in fixed position on said press, said second link member being connected to said hydraulic valve, said valve being connected in circuit with said pair of hydraulic rarns for selectively controlling flow of hydraulic fluid thereto.

3. A levelling control for a press as claimed in claim 2 wherein said torsion member is a torque tube.

4. A levelling control for a press as claimed in claim 2 having a pair of limit switches operatively connected one to each end of said torsion member and adapted to be actuated by twisting of said torsion member, each switch when actuated being adapted to cut ofi the supply of hydraulic fluid to its associated hydraulic ram.

5. A levelling control for a press as claimed in claim 2 wherein said moveable platen additionally is provided with a pair of switch members attached one at each end thereof, a pair of limit stops attached to a fixed point on the press, said additional switch members being each adapted to be actuated by said pair oflimit stops, both said additional switch members when actuated being adapted to reverse the direction of travel of the moveable platen. 

